1. Field of the Invention
This invention relates to a device for the filtration of a complex liquid such as blood, in particular able to be integrated in a device for processing blood for the purpose of an autotransfusion.
2. Description of the Related Art
It is known that the filtration of blood so as to remove impurities or certain compounds in particular in the case of an autotransfusion poses numerous problems, in particular the clogging of filtering surfaces.
The pores of these filtering surfaces are modified as the filtration conditions proceed, although the filtration flow rate decreases until it becomes zero.
Hereinafter, the example that is adopted is blood, which is a heterogeneous medium, the filtration device according to this invention being applied for any liquid composition that has identical problems. Thus, the presence of proteins of more or less significant molecular weights as well as cellular elements is found in the blood. If a filtration threshold is provided to eliminate them, these protein chains and cellular elements will block the pores of the filtration surface preventing the passage of elements to be filtered, and even water.
It is also noted that the permeation in the existing membranes occurs perpendicular to the surface, whereby the liquid volume that is to be filtered is placed above the membrane, and the filtrate is below. Placing under vacuum also makes it possible to promote the passage unless clogging occurs, because then the negative pressure promotes the plating of the clogging layer and on the contrary emphasizes this phenomenon.
This phenomenon can also be aggravated by the deposition of certain elements that compose the liquid phase that is to be filtered. In this case, gravity has a tendency to make these elements accumulate on the filtering surface, accelerating the clogging phenomenon, all the more if there is negative pressure. One solution would consist in stirring the composition that is to be filtered, but this is not easy to achieve if simple systems are sought.
If it is desired, for example, to integrate such a filtration device, for example in an autotransfuser such as the one that is described in French Patent Application No. 2,874,327, such stirring means are not conceivable.